Digital Ding Inspection Device

ABSTRACT

Inspection of an interior bottom of a borehole by means of measuring the sediment thickness at the bottom. A digital inspection device to be lowered in the borehole supports an electrical transformer for the continuous measurement of the sediment thickness at the bottom of a borehole. A digital readout unit receives signals from the electrical transformer and displays the bottom sediment thickness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 12/888,500, filed Sep. 23, 2010, the entire disclosures of which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH (IF APPLICABLE)

The invention was not made under a government contract, or federal fund.

BACKGROUND OF THE INVENTION

As a critical part of the drilled shaft quality control (FHWA, 1999), inspecting the bottom cleanliness of drilled shafts has always been challenging to contractors, engineers, and field inspectors, especially in the situation of the wet construction method, when direct visual inspections are impossible. Even with the dry construction method, inspectors have been reluctant to inspect the bottom visually due to safety concerns. On the other hand, most federal and local agencies, such as states' department of transportation and city building authorities specify that drilled shafts be inspected for bottom cleanliness prior to the placement of concrete. Typically, a minimum of 50 percent of the base of each shaft should have less than 0.5 inch of sediment at the time of concrete placement, and the maximum depth of sediment or any debris at any place on the base of the shaft is not allowed to exceed 1.5 inches. Conscientious cleaning of the bottom of drilled shafts has been proven by loads tests to be necessary for suitable load transfer in end bearing.

Currently, the Shaft Inspection Device (SID) or Miniature Shaft Inspection Device (Min-SID) are the only devices recognized as being relatively accurate to measure the drilled shaft bottom sediment without an inspector's direct measurement in the hole.

SID was developed in the early 1980s by Schmertmann and Crapps, Inc. The SID comprises a television camera sealed inside a water-tight jacket and is used for inspecting both dry and wet excavations. The concept of the SID was derived from an Australian drilled shaft inspection device originally developed by Dr. Jim Holden of the Country Roads Board. SID is a heavy (over 1000 lb) and large equipment. The operation is relatively expensive and time consuming

Mini-SID was introduced around 1998 with much lighter weight and easier operation procedures. However, it is still very expansive and time consuming It also involved the operations of specifically trained personnel.

Ding Inspection Device (DID) was developed around 2009 and was granted a U.S. Patent on Apr. 10, 2012. DID provides a simple, reliable, and effective way for the inspection of the borehole by means of measuring the sediment thickness at the bottom of a borehole. However, the measuring unit must be retrieved from the bottom of a borehole and a manual reading must be taken and recorded for each reading, which could be relatively labor intensive. In addition, the connection between the center steel piston and the sliding could be worn out quickly due to the repeated measurement, which could affect the accuracy of the measurement.

For these reasons, a digital inspection device with improved efficiency and accuracy is desired.

SUMMARY OF THE INVENTION

Embodiments of the invention overcome one or more deficiencies in the prior art by using digital position sensor instead of mechanical gauge. The entire measuring unit in the prior art, including the steel piston and the sliding collar, is replaced with a position sensor, which provides continuous measurements and digital readings of the sediment thickness at the bottom of a borehole without the need of repeated retrieving of the measuring unit.

The improved device provide following benefits for the drilled shaft inspection:

1. No need of the human excess into the boring hole

2. Significantly improved efficiency of the inspection

3. Significantly improved accuracy of the measurement

4. Continuous measurement with a digital readout unit

5. Easy to operate

DESCRIPTION OF THE DRAWING

FIG. 1 is the schematic sketch of the measuring unit.

FIG. 2 is a picture overview of the measuring unit.

FIG. 3 is a picture of the digital readout unit.

FIG. 4 is the design details A.

FIG. 5 is the design details B.

FIG. 6 is the design details C.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, FIG. 1 illustrates the schematic sketch of the digital Ding Inspection Device (DID). As shown, the system comprises a metal upper plate, three metal legs attached to the upper plate, a position sensor attached to the upper plate, a metal bottom plate with holes, three metal eye bolt lifting rings attached to the upper plate, a digital readout unit, and a cable connecting the position sensor and the digital readout unit.

To perform the inspection, the entire measuring unit is slowly lowered into a borehole. Once the unit reaches the bottom of a borehole, the bottom plate stays on top of the sediment and the three legs penetrate through the sediment and touch the harder surface. The relative movement between the bottom plate and the tip of the three legs is measured by the position sensor and displayed by the digital readout unit outside the borehole.

FIG. 2 and FIG. 3 are the pictures of the measuring and the digital readout unit.

FIG. 4, FIG. 5, and FIG. 6 are the design details of the measuring unit.

The inspection procedure includes following essential steps:

1. Align the key with the keyway in the connector and measuring unit. Insert the connector and tighten the nut to secure the connection.

2. Connect the cable to the digital readout unit and tighten the nut.

3. Connect the power source (110V/220V) to the digital readout unit and turn the power on.

4. Slowly lower the measuring unit into a borehole. If there is liquid in the hole, make sure that the measuring device sinks into the bottom by its own weight.

5. Take reading that is displayed by the readout unit

6. Lift the measuring unit to make sure that the tips of the three legs are on out of the sediment.

7. Repeat steps 4 to 6 if additional readings are required. 

1. An improved inspection device comprising an upper metal plate, three legs attached to the upper plate, a position sensor attached to the upper plate, a digital readout unit, a cable connecting the position sensor by a waterproof connector and the digital readout unit, a bottom plate with holes, three lifting eye bolt rings attached to the upper plate for insertion into a borehole for measuring sediment thickness at the bottom of the hole.
 2. A method of inspecting a borehole, either dry or into a liquid, by means of measuring the sediment thickness at the borehole bottom using said device of claim
 1. 3. The improved inspection device according to claim 1 wherein the upper plate comprises a round metal plate and three lifting eye bolt rings attached to the upper surface of the plate.
 4. The improved inspection device according to claim 1 wherein the three legs comprises metal bars with sharpened tips.
 5. The improved inspection device according to claim 1 wherein the position sensor comprises a device for measuring displacement, said displacement representing the sediment thickness at the bottom of a borehole.
 6. The improved inspection device according to claim 1 wherein the digital readout unit comprises a computer having a display, responds to the signals from the electrical transformer for displaying the sediment thickness at the bottom of a borehole.
 7. The improved inspection device according to claim 1 wherein the cable connects the digital readout unit and the position sensor with a waterproof connector. 